Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word for each of the blanks from 25 to 29. Fill in the appropriate word in question 29 In recent years there have been many articles on air pollution in newspapers and magazines. Scientists all over the world have warned that our atmosphere is (25) ______ more and more contaminated, and that Man, through his carelessness, may run out of pure air to breathe. Automobiles and industries mainly ...

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word for each of the blanks from 25 to 29. Fill in the appropriate word in question 29

In recent years there have been many articles on air pollution in newspapers and magazines. Scientists all over the world have warned that our atmosphere is (25) ______ more and more contaminated, and that Man, through his carelessness, may run out of pure air to breathe.

Automobiles and industries mainly account (26) _______ air pollution in most cities. They pour into the air such gases as carbon monoxide, sulfur and nitrogen oxides, (27) _____ are very harmful to humans. (28) ____ still, these gases, a series of chemical changes, turn into toxic acids. They fall down in “acid rains”, raising the acidity in the air, soil and water to dangerous levels and affecting not only tress but also fish and other wildlife. Many industrial countries in Europe and North America have suffered bad effects (29) ______ those “rains”.

Surely, Man faces no more urgent problem than that of saving his own survival. Scientists, social organizations and governments shout sit down together to solve the air pollution problem.